TMF Introduction (G06.26+)

Transaction Protection and Database Recovery
HP NonStop TMF Introduction—522414-002
3-16
Summary of Transaction Protection and Database
Recovery
Summary of Transaction Protection and
Database Recovery
Database files in a modern transaction-processing environment must always be
available: when they are not, businesses can lose revenue.
Downtime can be avoided by using hardware such as fault-tolerant disks, achieved by
methods such as disk mirroring, and fault-tolerant disk access, achieved through
shared disks. When a disk for a mirrored pair fails, the system uses the good disk
volume for the application while the damaged volume is being recovered. Mirrored
volumes preclude many recovery problems caused by a single disk failure.
Other sorts of downtime can be prevented using software. TMF protects applications
from downtime in the event of process, processor, or system communication failures.
It offers two levels of protection for applications, depending on the recovery
requirements of the application and the amount of system resources that TMF can use;
these levels of protection are TMF transaction protection and database recovery.
TMF Transaction Protection
Audited database files automatically receive TMF transaction protection, including
transaction management, database consistency, and database recovery.
The resources and requirements for TMF transaction protection are:
•
Application code that includes transaction control statements to begin, end
(commit), or abort (back out) transactions, and appropriate data-locking techniques
for the transactions.
•
Sufficient disk space for audit trails.
Database Recovery
Database recovery includes TMF transaction protection and full protection of database
files through file recovery.
TMF provides the facilities for file recovery, but using them to protect the database or
portions of the database is optional. Business requirements should determine the kind
of protection the database needs. Site personnel then must ensure that there are
sufficient system resources to support TMF requirements.
In addition to the resources needed for transaction protection, database recovery
requires the following resources:
•
Procedures and storage media drives for making:
°
Audit dumps
°
Online dumps of any file to be protected by file recovery
•
A fireproof vault or safe place off-site for storing the audit dumps and online dumps